The maintenance of complex reproduction machines has become an increasingly important aspect in the commercial production and sale of such machines. As these machines grow larger, more complex, faster and more expensive, it has become increasingly important to take measures ensuring the machine's continued reliable operation. As these machines are indispensable to their users, an increasingly important feature of such machines is their reliability. When the machine does malfunction, it is desirable that it be fixed in as short a time as possible.
As a result of these needs, much work has been done to improve the on-board diagnostic capability of these machines. With such a machine capability, a service representative, or a trained user can easily and quickly determine the cause of the malfunction. In the case of a service representative, based on such a diagnostic report from the machine, action may be taken to effectuate an appropriate repair.
In the past, such diagnostic capability was restricted to use during a diagnostic mode of operation. In this type of system, as shown by U.S. Pat. No. 4,477,901, assigned to the same assignee as the present invention, a diagnostic system is provided for use by a service representative when the machine is not in a normal mode of operation. In such a system, the service representative can exercise certain diagnostic capabilities of the machine particularly related to the flow of paper through various paths of the machine to determine whether such paths are operating at the appropriate speed, while the machine is in a nonoperable mode. Alternatively, a limited examination of paper flow paths may be made on a real time basis demonstrating the events leading to a malfunction, as shown by U.S. Pat. No. 4,335,949, also assigned to the same assignee as the present application. This information is lost after the problem has been corrected and operation of the machine is resumed. Often, difficult and costly problems occur only on an intermittent basis, and are difficult to replicate. Accordingly, the service representative has no information to proceed from when asked to make adjustments on a service call.
In the same manner, U.S. Pat. No. 4,268,746 teaches comparing actual machine operation, i.e. paper passing times, with an ideal system, and creating an alarm when the system varies more than a selected amount from the ideal. Similarly, U.S. Pat. No. 4,249,080 teaches a system for comparing detected article movement with detected surface movement. Such systems provides for detection of failure events, but not for the factors leading up to the failure event so no corrective action may be taken based on the machine malfunction indications.
It is understood that the diagnostic system of the IBM Series 3 copiers, Models 30, 40 and 60, provides stored information for later retrieval regarding the location of paper jams occuring over time, as well as the source of paper causing the jam. This identifies the paper path which is potentially at fault, but tells a service representative nothing about the cause of the problem.
Xerox Disclosure Journal, Vol. 9, page 393, November/December 1984, discloses use of an adaptive algorithm for recirculating document handlers which entails using sensed document acquisition time and sensed document transport time to control the total time through the recirculating document handler. The acquisition and transport times described are sensed for each set of documents passed therethrough, and abnormalities can thus be detected.
None of the references teach a satisfactory way for a service representative to examine past successful operation of the paper paths as well as past fault operations to determine whether a problem is spontaneous or developing over time. The prior art methods of diagnostics have proven unsatisfactory in the area of preventive maintenance as previous systems have relied on the appearance of a malfunction of fault to begin the diagnostics operation, or require the service representative to work backwards from a fault to determine its source. It would therefore be desirable to provide a constant operation, real time diagnostics system, accessible at any time, and providing current operation information on a portion of the machine, as well as information on previous fault operation.